Pod::ToDemo allows you to write POD-only modules that serve as
tutorials which can write out demo programs if you invoke them
directly. That is, while SDL::Tutorial is a tutorial on writing
beginner SDL applications with Perl, you can invoke it as:

  $ perl -MSDL::Tutorial=sdl_demo.pl -e 1

and it will write a bare-bones demo program called sdl_demo.pl based
on the tutorial.
